A difficult question to answer - I guess it depends on your preferred workflow and how you used Fireworks. Fireworks, no matter how you looked at it, did get quite old in the teeth - workflows have changed quite a bit nowadays, and FW was not keeping up. Adobe is, I think, hoping to have Photoshop replace it. But that is not quite the best option right now.

I found a good replacement in Photoline, although it is still missing a couple of things crucial to web dev. The good things are full svg support (import and export), export of (selected) layers, pages, good (real) vector tools, pixel alignment for vector layers, virtual copies of layers, excellent bitmap tools (comparable to PS), good guides, good alignment tools, patterns, a built-in procedural texture maker, document colours (newest beta), pixel view, anti-aliasing control per layer, great down-scaling algorithms, and so on. I use Qolor Quantizer and RIOT for web graphics optimization.

The things missing are: slicing (which I never used anymore anyway - all layer based workflow now); symbols (though virtual layers work as a workaround); a general pixel alignment setting; no html/css output (which I never need anyway).

It can do much more than Fireworks, but for pure web work it is still missing some things. The devs are very open to suggestions, though, and so far have been adding a lot of useful web functionality. It can only improve, in my opinion.

This works for me. I also work with Xara Designer Pro - which does have full html/css export if required. There is also Xara Webdesigner (Pro) (Designer Pro includes all that functionality).

It sounds like the perfect FW replacement. As a matter of fact, that project was started by disgruntled ex-FW users.

Of course, you could switch to Photoshop - but that is still too awkward for web work, in my opinion. Illustrator could also be an option. Even InDesign can be used for working web prototypes. But none of these are truly optimized for web work.

In short, do your own research; download the trial version, play around, and see if they do what you need in your web work.

Axure RP is a great option for making wireframes and working prototypes. Not so great for visual design or exporting to image files. I hear of people using Sketch 3, although I haven't since it can't export to PSD.

Personally, I've switched to Adobe Illustrator for my web layouts. I'll use Photoshop for raster manipulation, but Illustrator is great for pixel precision, 9 slice scaling, and multiple layouts with smart objects. My main beef is artboards—there should be no limit on the size, and adding and removing boards is a hassle. Which it worked more like pages in Fireworks.

Axure RP is a great option for making wireframes and working prototypes. Not so great for visual design or exporting to image files. I hear of people using Sketch 3, although I haven't since it can't export to PSD.

I dislike Axure RP myself - too convoluted, and it feels very clunky to me. I prefer Justinmind Prototyper myself - have you tested the newest version yet? Even the free version is rather useful.